/*
 * fnpathfind.c -- find file in a list of directories
 *
 * Part of publib.  See man page for more information
 * "@(#)publib-fname:$Id: fnpathfind.c,v 1.4 1994/07/16 15:28:42 liw Exp $"
 */

#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

#include "publib/fname.h"
#include "publib/errormsg.h"

/* XXX - there is a standard unix function pathfind ... */

int fnpathfind(const char *path, const char *tgt, char *result, size_t max) {
	char *p;		/* auxiliary pointer */
	char *colon;		/* where the next colon is */
	char *fullname;		/* the full name of the current possibility */
	size_t cursize;		/* current block size allocated for fullname */
	size_t fullsize;	/* size of current possibility (<= cursize) */
	size_t dirlen;		/* length of the current component of path */
	size_t tgtlen;		/* length of the tgt */

	assert(path != NULL);
	assert(tgt != NULL);
	assert(result != NULL);
	assert(max > 0);

	tgtlen = strlen(tgt);
	fullname = NULL;
	cursize = 0;

	for (; *path != '\0'; path = colon + (*colon == '\0' ? 0 : 1)) {
		/* find end of current path element (next colon, or the
		   trailing '\0' if last element */
		colon = strchr(path, ':');
		if (colon == NULL)
			colon = strchr(path, '\0');

		/* compute size of full name: 
		      dirname + "/" + tgt + trailing '\0'
		   except that the "/" is only needed if the dirname doesn't
		   end in a slash.  Then make sure fullname is at least big
		   enough.  */
		dirlen = colon - path;
		fullsize = dirlen + (dirlen ? 0 : 1) + tgtlen + 1;
		if (cursize < fullsize) {
			p = realloc(fullname, fullsize);
			if (p == NULL) {
				__publib_error("realloc failed");
				free(fullname);
				return -1;
			}
			fullname = p;
			cursize = fullsize;
		}

		/* construct the full name */
		strncpy(fullname, path, dirlen);
		p = fullname + dirlen;
		if (dirlen > 0 && fullname[dirlen-1] != '/')
			*p++ = '/';
		strcpy(p, tgt);

		/* does it exist?  if so, copy to result and return */
		if (access(fullname, 00) == 00) {
			strncpy(result, fullname, max);
			result[max-1] = '\0';
			free(fullname);
			return fullsize;
		}
	}

	/* we didn't find anything */
	free(fullname);
	return -1;
}